We work with numerical and theoretical models of star- and planet formation and proto-planetary accretion disks around newly formed stars. Molecular clouds are the large-scale supply from where stars are formed via gravitationally accretion of mass and angular momentum. The accretion process channels gas through a disk to the star in a delicate balance with the environment. We employ sophisticated computer codes, both at the local high performance computing center and at the largest computers worldwide, to deal with the challenges from understanding the large-scale environment to the microscopic growth of dust to planetesimals in circumstellar disks. This makes it possible to bridge the gap between molecular cloud scales, which determine the initial and boundary conditions for circumstellar disk accretion, and the microphysical scales, which create the conditions for planet formation.